Automatic telephone exchange system



June 2, 1931, J, scu 1,808,577

AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Jan. 11, 1930 10 Sheets-Sheeb 1 lNl/EN 70/? Jne 2, 1-931. F. J. SCUDDER 1,808,577

AUTOMATIC TLPHONE EXCHNGE SYSTEM v Filed Jan. ll, 1930 10 SheetsSheet 2 IHI' June 2, 1931. F. J. SCUDDER AUTOMATIC TLPHONE EXCHNGE SYSTEM Filel Jan. 11, 1930 1,0 Sh9ets-Sheet 3 HII June 2, 1931. F. -J. SCUDDER AUTOMATIC TLPHONE EXCHANGESYSTEM- Filed Jan. 11, 1930 10 SheetsSheet- -4 Ru m INVENTO/ June 2, 1931, F. J. SCUDDER AUTOMATIC TLPHONE EXCHANGE SYSTEM Filed Jan. 11, 1930 10 SheetsSheet 5 June 2, 1931. E. J. SCUDDER 1,808,577

AUTOMATIC TLPHONE EXCI ANGE SYSTEM Filed Jan. 11; 1930 10 Sheets-Sheet 6 'June 2,1931. .A F. J. SCUDDER AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Jn.

11, 1930 10 Sheets-Sheet 7 June 2, 1931. F. J. SCUDDER AUTOMATIC TLPHONE EXCHANGE SYSTEM 1,sos ,577

Filed Jan, 11, 1930 10 SheetsSheet 8 mm m June 2, 1931. F. J.fiCUDDER AUTOMATIC TLPHONE EXCHNGE SYSTEM 10 Sheets5teet 9 E ild Jan. 11, 1930 h \N/ r June 2, 1931. F. J. SCUDDER AUTOMATIC TLPHONE EXCHNGE SYSTEM Filed Jn.

10 Sheets-Sheet 10 Patented June 2,1931

NEW YORK AUTOMATC 'T-ELEBIONE EXCANGE=SYSTEV.

The invention relates to an automatie telephone system and more: particularly t0 a noveLmethodandsystem ofeircuits OI ufti-.

lizing equipment at oneoffioe in a large sexchangearea as overflow or auxiliary equipment for a pluratlity of other ofiioes in the same area. 7

VVhere there is a large number of telephone lines to be servedas is the case in most 1 eities,these lines are divided among a number of ofiices which together form what is known' as an exehange area. The.number of offices, ofeourse, is determined by the geograPhical distribution of the subscribers to be, serVed and by the density of the telephone deVelop- .ment in agiven section. In large eities'it generally oeeurs that certain :of-these oflices Will be grouped in sections in Whioh lines are used almost exclusively for businesspurposes and others Will serve lines which are used for 7 a variety .o:E purptses other than those which may be classed asstrietly business. Inbifices where business limes predOminat tbe'peak load is during business hours and aterbusi ness hours the load may drop off to @racti-' oally nothing whereas in residential districts the peak load is' often after business bouts,

There may be other local conditions which w0uld cause ;the pe-ak load in the -Variusoffices =to coeur at difi"erent tiines during the day. For example, referenoemay be made to the situation in New York City whre ofliesservingthe finanoial district in thelo w er art-cf the city are practioally -without 35 load after .five oclock whereas thepeak load in an Ofee serving the hotel and thatre district oomes on between seven and eight.in the evening.

It is the usual praotie in,oifioes which are i0 Worked on an automatic basis to provide suffieient equipfiient in the way of line finders,

seletors and control equipment to take care of the pzzk load. A Certain -p'er -cent .of this equipment is idle When the l0ad is at }its min-- imum. APparatus which =is idle is not Worked a-t a maximi u n eificiency and fixe d charges and depreeiation are present Whethei th eq{uipmeut is operating or not,

torsan auxiliary group of line finders Whili unk stock market isih session -nd ail the }rQgi1lai L to handle the average trfiic load and the auxiliary lino finders added in suflicient numbers to care for the pe.k 1oad. Since the line finders, districts, linksand senders, which are installedat the overfiow office needonly care for the overfioW from the ofiices to which it is common, the percentage of such equipment to the number of incoming trnks neednot be as great as the usual Percentage of such equipment supplied in the originating oflices. Thus considerable econom may be attained through the use of the invention.

A clearer conception of the scope and purpose ofthe invention -may be obtained from a considration ofthe following description in'c0nnectionwith the attached drawings in .Figs. 1 to'5 show apparatus at an office A of an exchange system; and

. Figsk 6 to 9 Show apparatus at an office B which may serve as an overflow oflice for a pli7ality of offices, such as ofiice-A.

'; 1 shows a calling subscrib rs line to- ..gether -withrelay equipment comrn0n t0 a r ter0flice trunks for handlingoverflow ca1ls,

the. district selector of Fig. 8

group of fines;

Fig. 2 shows a start circuit and a selectingv,

switch forselecting idle lin finders and in- Fig. 3 shows a line finder and district se- 7 Fig. 4 shows a link circuit for associating a sender dia.grammaticall,illustiated with thdistrirtsiector ofFig. 3;: j 7

Fig. 5 shows an auxiliary line finder individua1 to an interoifice trunk having access to the calling line of Fig. 1 during periods of P a 7 Fig.6' shows a calling subscribers line togetherwith common relay duipment termingiting in oflice B and an interofii'ce trunk;

- Fig. 7 shows a start circuit;

, Fig. "8 "shows a 1'ne finder district selector; v

Fig; 9'shows a link circuit for associating a sender diagrammaticaliy illustr Fig. 10 is a digram showing how the several figures should be arranged to illstrate the complete circuits of the invention; and

5 Fig. 11 is a schemati0 drawingilluStrating the principles .of the invention.

The invention has been embodied in a dis closur, which is substntialiy like that of Patent No. 1,690,206, granted to A. Raynsf0i'd, November 6, 1928. The snders diazgrammatically indicated by small rectangles inj'the upper left corner of Figs. et and 9. are

Ofthe character disClosed in the Patent No.

1,589,402, granted' to 0. H. Kopp,J une 22, l926,and reference to the Kopp patent may be, made for operations not fully described h r '1' As in ,the discosures of the aboVe gmentiohed patents, a pluralitbf link circuits is provided at each exchange ofiic arranged to ated with serve a group of calling lines and are taken into service in rotation. .When a link circuit compltes its function it hunts for and associates itself with, a district selector which iS ready for use and the link and district remain in a suballotted conditionimtil'the'next' link in the series has been putihto service. The link circuit is then placed in an ailotted position. from which it wili be advanced ,by'

the initiation of a call and theaction of the .ssociated start circuit. Forexample, the

' trip circuit of Fig. 1 and start circuit of Fig.

2 are so arrahged that only one line'of a group of lines-ma}rbeservd at a time and so thatthere may be -cooperation between two subgi*oups of fines tofieach of which thegroup tails of its functions forin no particular part of the present invention and are fu1ly de- Scribed in Patent No. 1,567,072, granted to W. H. Matthies,Dember 29, 1925! The start circuit 01 Fig. 2, however,;dif fers from the start circuits of the above mentioned patehts'in that it is provided with a.

selecting switch which selects an id1e line 'of1ink circuits of Fig/Lis indiVidual. The der finder of an auxiliary group of Iinefinders niounted on the same 1 ine finder frameas the regular linefinders which serve the caliing 1ine group. One of these auxiliary line finders is disclosed in Fig. 5. The start circuit is so arranged that in the event that atthe 1 time a "call .is initiated in the line group in whichthe calling 1ine is 1obated, the trafiic is so heavy that there are no links and reglar liriefinders available in the group n0rmally arrariged for giving first choice Service for the -call, an auxiliarv 1ine; finder will he started toconnect' with the callihg line'to trunk the 'cal1 over an interoffice trunk.to the overflow ofiice. &s stated hereinbefore, the auxiliary 1ine finders such as the line finder of Fig. 5 are m0unted upo-n the same frame as the regular line finders, one ofwhich is shown inzFig.

3. andthe brush tripping. magnets, one of which is shown at 303 in Fig. 3, serve'both the regular and auxiliary 1ine finders in common. The1ine finder of Fig. 5 is individual to an interofiice trunk which terminates as a 7 caliing 'line in the.terminai banks of a group of 1ine finders inthe Overflow office. One of the groupv of line.findersin the overflow of fices.

Referring PaitiCularlyto Fig. 11 in which apparatus of an Ofiice A and an overflow office B of an eXchange system have been peri0ds from a pluraiity of riginting of sclienatically illustrated, it will be assumed tira-t oflice A is arioflice in Which a pek load may occur at a tiirie when the regularloadf in the overfiow oifice B 1s lrght. oflice.

A the line finders 300, serving the group :of subscribe'rs lines in which limes 100 and 150 are located, aie paired in the usual mariner with district selectors 350., 'The line 'finders in the ieit half of the line finder -frame are arranged to be started through the startc1r-' cuit 250 and a pr-e-allotted link of the A group of link circuits 1100 and the line find ersin the right half of the frame are arrangcd to be started throug-h thesame start circuit 250 and a preallotted linl: of the B group of link circuits 1101 in accordance with the practicesct orth in the above mentioned pat ents. In accordance with this invention each" half of tlie line fiiidr frame 'is also equipped with auxiliar lino finders, such as 550 and 560, which are individrial rspectively to interoifice trunks 555 and 565 terminating as clling lines in the banks of lino finders 880 of the overflow ofice B. These auxiliary lino finders 1nay for example be s'ubstituted for certain of the regular lino finders.

' At the oifice B, all 0' the line finclers .880 in both halves ofthe lino finder-frame serviirg a group 01 subscribers limes including lines 600 and 650 and tlie interoflice trunks 555 and565 are paired in the usualmanner witlidistrict -'selectors 890. 'The line finders of the left liaif of the frame 'are arranged to be.started through the -start circuit 750 and rided individual to the 'start circuit 250 which Selcts an idle line finder 550 or 560 for use at such times as the oficeA reacheS a peak load conditi0n AssoCiated With the start circuit and common to the linkcircuitsof the A group is a relay 206, A similarrelay 207 is provided common to 'the link circuitsaf tlie group. VVhen all of the link circuits of the A group are bus, a circuit is established over the cai71s 424424" ofthe link circuits of theA group fofrelay 206 Which disconnects the start circuit 250 ,romthe linl: circuits of the A group-and entends 1t to the windingof relay 208. The rela 208, in turn, controls the closureof the start cir- V cuitto a line iinder such as 550 or 560. When ail cf the aiiXiliarylinefinders have been' placed in service, a chainicircuit is establislied thrcuh contacts of rlas 513 of those 5 b 1 o -n l1nl: circuits th rough the wmcung ont relay 21 1; i Relay 214 upon oprating With reia function to serve lines in the subgrop in Which line100 is located until :after all of the links of the A group and all ofthe auxiliary lino :finderslmve been placed in service;

Similarly,When all of thelink circuitsof the B group are busy a circuit is establishecl over cams 112A 1124 of thelink circuits of the B group -for rlay 207 which disconnects the start circuit from the-B group 'of links and connccts it'to a winding of relay 208.

Rela 208 then=functionsto start auxiliary these line findrs have been placed in service, relay 214 operates, in turn operating relay 222 -Which transfers thestart circitto'the A group oflinks. Thus the Agroup of links cloes ,not function to serve lines in the. subgroup in which line 150 is located until all of the links Q- -t ie'B group and all of the auxiliry'line finders' have been placed in service. u

Referring nowto Figs. 2 to 9, inclusive, oi the drawings silice under coi1diti0ns:of normal load tire apparatus i ofiice A functions in the well-known manner :Eully set forth in the patents above reierred to,it will not be necessary to desCribe herein in detail, tire manner in which a call is extended from the substation 100 to a desired subscribers line.

It Will ther ore be assurned that at the tirr1e -the subscfiber cf substation 100 initiates would'ordinarily be available" for'use, are

icc

busy because o a peak load condition. One

link circuit of the A group of link circuits g'ivingfirSt choice service to the subgroup of WOhU1lIBl lines in which the line 100 is located is disclosed in Fig. 4 together with certain sequenee switchcamsof other link circuits of the saine group. VVhen all these link circuits are {busy 'their sequence switchcs Will be standing in some position other than 1 or 10, which are normal positions, and thus a ser1es'crrci11t Wlll be established :rom ground throughth contacts of cams 424*424, 424, conductor 205 5 to battery through tlie'leit windingof relay' 206.

VVhen relay 206 operates, a lockingfcir cuit is establishedtherefor extending from battery througli the right -winding andright front contaCtof relay 206, theinner ieft normal Contacts ofrelay 203, the left back contact of rela 202, conductor 131,' the'inner leftcontact of relay 103, the outer left contact 'of relay 108 to ground at the ieft c0n tact cf r elay 110, relay 110 being operated vhn tlie strbstationl00 initiated thcally The locking ground for rela 206 is now extended through the right winding of 'relay 208 to battery, thus operating relay 208. Re-

lag 208 establishes a start circuitfdr theline findor of Fig. 5, it coing assumd that soloctor r 200 is'at tho timo standing in a position t start that lino findoi. This circuit'may bo conductor 503, brush 209, Winding. of rolay 210, contact of rola208, conductor 211, to

7 net 212 of tho soloctor gr0und at tho right back contact of relay- A circuit is also closod in parallol from V 5141 groundon conductor 211 ovor tho contact cf folay 208, tho back contact of stopping mag- 7 200 to battory through tho winding cf rolay2l3., Rclays 501,210 and 213 theroupon oporatc, but tho oporation cf rolays 210 and 213 is without o1fcct at this timo.

Rclay 501 uponopcrating looks ovor its onorgizing circuit to battory at its outcr loft contact indopondontly of tho contacts of rolays 502 and 515,at its' enter right contacts oStablishcs a bridge across tho outgoing conductors 620 and 621 of tho intorofiico trunk 555 for a purposo t0 bo lator doscribod, and at its 'innor right contacts ostablishos a circuit oxtonding from battory through tho winding ojf rolay 500, normal commutator Segment 508, brush 509, brush5l0, commutator strip 511, to ground.at tho innor right contact of rclay 501. Rolay 500 operatos in this circuit and closes obviouS circuits for tho up drivo magnot'5l2 and for rolay5l3.

Rolay 513 upon oporating closos at its right front contact alocking circuit for itsolf oxtonding thr0ugh tho rolay; 514 to ground at tho loft back' contact of rolay 515. Rolay 514 boing shuntod by ground at. tho contact of irolay 500 doosnot opcrato in this locking circuit as long as rolay 500 romains criergizod. Tho lino findor of Fig. 5 undortho control of magnet 512 now moves upwtrdly and sinco trip magnot 303 is operatod, tho propor set of brushos is trippod. At its loft contact, rolay 513 closes ono point in a chain circuit oxtondin through contacts of similar rolays cf auxiliary lino findorsfor apur. pose to be later explainod.

As soon as tho lino findor loavos normal, a

locking circuit is providod for rolay 500 oX- tonding from battory through the loft contact of rolay, 500, tho back contact cf relay 516, conimutator strip 517, brush 518 to ground ovor brush 510, strip 511 and tho innor r1glct contact of rolay 50lwhich holds rolay 500 oporatod, As soon as tho commut2itor:-brush 519 ongagos segment 520, a Circuit is closod from ground ovor brushos 510 and 519, sogmont'520, conductor 2l5,'contaCt 232 of koy 204, innor right front Contact 0f rolay 201 toconduCtor-l29 and tho right Winding of relay 201. This circuit shunts tho loftwindir1g cf rolay 108 and causos that ro- 7 lay to roloaso, in turn roloasing tho trip magnot 303. NVhon brush 519 loa'vos segment 520, tho circuit of relay 201 is oponod and that re loasos rolays 210, 213 and 501. VVhon tho lino 522, which isconnectedtoconductor 114 and thorof0ro to battery through tho right wind- 1ng of rolay 109, a circuit is complotod from this battory through tho winding of*rolay 516 to ground. Rolays 109 and 516 oporato,

rolay 516 oponing'thoholding circuit proviously tracod for relay 500. As soon as tho, brushos of tholino findor'bocomo accuratoly contorod on thotorminals of tho calling lino,

a second holding circuit extending from battery through tho winding and loft contact of rolay 500 ovor commutator strip 523, brushcs 509 and 510 to ground, is openod at an insulating segment of strip 523 and rolay 500 roloasos, oponing tho circuit of up-drivo magnot 512 and romovos tho shunt ground from tho winding cf rolay 514 WhiCh now operats in tho locking circuit of relay 513.

findor brush 521 makes contact with terminal L Rolay 514 upon oporating, opens tho circuit of rolays 516 and 109, at its outor right contact romovos ground from conductor 211,. and ostablishcs an obvious circuit for rolay 507, ostablishos a circuit for tho out-0E rolay 102 ofthe calling lino oxtending from battry ,through tho windings of rolay 102, conductor 112, terminal 524 and brush 525. to

ground and at its loftfront contact proparos n a circuit for tho calling lino messago rog1s tor118. Rolay 109 Which oporatodin s'orics with rolay 516 opens/tho holding circuit of rolay 110, thox*oby rostoring tho rolay oquip nient of Fig. 1 so that anothor Callnglino in tho samo lino group may have accss to tho ,common start circuit for starting anothor doonorgization of rolay 501 and atits lowor innor and uppor transfor contacts, roplacos 1 w tho bridge through thooutor right contacts] of rolay 501 by a bridge cxtonding ovor brushes 529 and 530 and tormihals 531 and 532 of theline findor, conductors 117 and 116, and tho calling substationloop.

At tho timo rolay 501 oporatod totablish a bridge across conductors'620 and 621 of tho otgoing end of trunk 555, a circuit Was cs-* tablishod for lino rolay 622 at tho distant end V of the trunk which may botraced from battory through tho winding of rolay 622, right back contact of Cut-ofi' rolay623, thonco over conductor 621, tho. lowor normal contacts of rolay 507,tho router right contacts of rolay 501, tho uppor normal contacts .of'rolay 507 tact of rolay 623. Aftor tho oporation of relay 507,rclay 622 is hold onorgizod over the calling lino loop; Rolay- 622 in'oporatin'g closes a circuit from battory through-r sist anco 604, winding of rolay 603, to ground at tho right contact cf relay 622, It also proconductor 620t0yground at tho loft back conpares a circuit from bztttery:througfl rcsis tance 611 and the rightwindingcf relay 609 in parallcl, left front contact: et relay 622 to conductor 624 toidentify thecalling tnunk of the line finclershaving access to 'that' trunk.4 Relay 603 in opera ting closes a circuit from battcryoVer the back contact of nerloft front contact and left winding of rclay 608 to gnoundat the innr riglit back contact of relay 609. Rlay*&closes a cir cuit f=rom ground at its outer right front contact through the winding of trip magnet 803 of the lincfinders of thc frame serving thc sulegroup of fines in which thetrunk 555is located to batteny in preparation for trippingthc proper set of'brushes ofthe line .finder. Relayfl openates in the locking circuit-ct relay 608 andin combination there- With closes a circuit .froni ground over its outer right contact, jonductor 628,lcft mid elle contact of rclay 608, 'Winding o f relay. 610 tobattery. Rclay 610locks over its right contact to ground at the outen back:contact of: relay 609and closes; a circuit forstarting an allotted lime finden. It;Will be assumed that thcsequence switch 900of thelink circuit 01 Fig. 9is' at the timestanding in posi' tion 1 and is connectedwith thc pne'2illotted district selector 890, the sequencc switch: 800 of Which is standing in position 2. At this tine the openati0n of relay 610 Will thcrefore close a circuit fron ground at its{lft contact, tlie outer left contact of relay 608, the inner lef't contact 015 relay 603, conductor 631, l'eft back contact of'rclay 7 O2,inner left back contact of relay 703, conducton 706, a A 7 802 to groundover: thelowen left and uppcr lowercontactsofcam 903, bnush 902, terminal 901,conductor 878, the lower left and:,upp r right contacts of canu 801, the windingof relay 802 to battery; r

Relay 802 in opcrating,

drive magnat 804 of the line findcr,innt}i right front contact of'rlay802,.riglit concircuit is providedfor. nclay 802c wtcnding oven its inncr loft front contact,the upper;

night andlower loft contacts et cam4 8107., ,the bacl: contact. of relay :856; commutatomstrip closes a circuit, from battery through the winding;of up- 85Z, brush 858 to. ground which nolds nclay 802 5peratdindependent cf the trip'cincuit.

As soon as cmmutator bruh 0szgtaggs segment 809, a Ciifiuit is closcd, fronu ground ovcr brush 808-,3sgrflcht 809,,lower contacts* et cam 810,; conductor contacts: 732 of cuit of relay -opcned and'-tliitfcly nclcascs,. tnecing the start circuit. :Wlicn terminal 882 which Conncted t'o conductor 624 and t hcrefotetobattery, acircuit i's' corti- 848to gtoundl Relgty;856 operates tlis circuit and closes a shunt aroundiits windixi'g tln;ough resistancc 811 to* grundovcr com-' ingcircuit of relay 8022 Tlicopration{of contacts of caih832 toiground at thej'uppc;

,tending froin battry at its'lft front[con At thc ttmcrelay 802 operated, it cl Sd a circuitfron groi ind .atth upperleft contact of squence 900,uppofc9htfst .of ain9l2 to.ground .at the outorright front contact cf relay' 909 advancing linksoquonco Lswitch 900 to' position 2. 'Whon s'oquonce switch 900leavos'position' l,rolay 909 roloas's, In position2a circuit is clsod fr0m battry through tl1o Winding of .rolay 913, "right Contacts "cf ca'm 914, loft backcontact of rlay9l5 to ground at the lower loft con- Rola 913 also clososa Circuit from battory' 'throgh' the middle winding of rolay 915, 'uppor contacts of am 921, right Winding of rolay 915, to ground at tho innof right'con jtact of rolay'9l3. Tho curront in this circuit findor 920,

'right contact- "but doos 'croaso a a, circuit -from battery thiough the right closes a circuit from battery through the magnet9l 8 in soarch of an idlo sonder.

howovor, is not sufiiciont to oporate relay 915 flux in tho 'Winding of that r rolay so that it bocomos quickto opoiate whon tho test circuit is closed. The test circuit oxtond's from :brsh 922, upporcontacts of cam 919, loft back contact of iolay 909, loft Winding of rolay 915, loWor riglit and upper loft contacts, of cam 921, .to grond at the inner 'right contact"ofrelay 913. An idlo sonder is characterizod by battorypotontial on engags. tormintl923 tho abovo tracod circuit is corrlplotod and rolay 915 opor*ates quickly, closing a lcl zing Circuit for itsolf frombattorythrough'its iniddlo xzvii1ding, the upper contacts o f Gain 921, and right front contact -ofrohy9l5 to ground. It also opens tho circuit"of.relay 917 which rolea'sos to in turn r{loaso' m'agnot 918 and bring the 1 sonder idlo sonder. Tho reloso of rolay 917 in turn findor920to rest on the torniinals, of the reloasoslrolay 9l3. With rlay 913 roloasod and rolay 915 oporatod, ia circuit' is closod from bittoiy through the winding of soquonco swit Ch magnet 900, uppof loft contact of cam 197 6 contacts 927 of jack 928, loft back contact foi iolay 913,lcft front contact of relay 915,.t0

ground attho loWorlef't contact'of cam 916, thus advtncing soquonco sWitch 900 topositiori3.

AS soon as 'soquonce Witch 900 'roachod a circuit was ostablishod from ;l0Wer'loft contactof cam 823, the uppor right contact of ca'm824 to battory throughtho loft wii1ding of rolty825. Rola 825 upon 0porating with r olay 8021*oloa sod, closes a cir ,C'uitfor advancing soquonco switch 800 into position-3a This circuit entends from battory mayv bo tracod 940, brush.94l, tho lowor contact of cam 929, brush 978, terminal 977, conductor 822. the

, thozright contact :of cam 929,-

- sl r 978, terminal 97 7 conductor 822,-the

tlirougli 'thoiizvinding of'soquone sivitch mag net 800, thouppor right contact of cana 826, f

the right front contact of rolay 825,tho loft back contact of relay 802 to ground 'at the upperleft contact of cam 836. Whon sofrom the ground attho sonder 0Vor terminal 930, brush 931, the lower coiitactof .cam 934, brush 932, terminal 933, conductor 819, the lowor contacts of cam 820 to battory thro1igh tholowor winding cf rolay 814 and in parallol thorowith 0vor the upper leftconfqunco switch 900'roachos position 3, a circuit 7 is closed tact of cam820 t0 battory through the wind- 7 ing rolay 821., 'Rolay 821 oporates although A inoffoctivo at this timo, butrela 814 being marginal, doos not oporate.

As,soon as sequenco Switch 900 arrivod in position 2% it-proparod tho pulsing circuit for rocoiving dialing impulscs; This circuit from the sonder ovor terminal loft contact of cana 815, the uppor back contact cf rolay 8l4,'brush 885, torminal" 886,

Conductor 620, uppr tltornatocohtacts of rolay, 507, brush 529, terminal 531, conduct0r "117, ovortho' subscribors lino 100p and through lois dial roturningovor' corlductor 116, terminal 532, brush 530,-tho innor lowor alternate contacts.of ro lay 507, conductor 621, terminal 887, brush 888, thoinnor lOwor back contact of rolay 814, through the winding cf siipo'rvisory rola'y 827, the loft contact cam -816, 'cOnductor 828, torminal942, brush 943, the uppor contacts of cam 903, brush 944,

terminal 945 to the sonder. Upon theostab- "lishinont 'of .this pulsing circuit, a dialing tono .istransmittod to the calling lino in the well-knowri mannor to inform tho calling Subscriborthat tho sonder is roady to receiVo impulses which ho may thon sond out by manipr ulating his dial.

' Upontho so1zuro of the sonder, battory is .romovod from terminal 923, thus'reloasii1grola 915 whichcloses a circuit for advancing tho soquonce switch 900 into position' 5. This circuit may 'bo tracod fr0m battory through thewinding of magnot 900, -theuppofri ht Contact of cam 976, the loft back contact of rolay 915 to ground at the lowor loft contact of Cam 916. Soquenco switch 900 romains in position 5 throughout the furthor oporation of the sonder. As soon as the calling subscribor has dialodtho office code digits of the dosired lino numbor the sonder establishosa fundamontal circuit for n controlling the district soloctor of Fig. 8

which may' be traced' from' battory through 'the loft winding cf rolay 825, the uppcr right contact o-f cam 824,-tho upPorloft contact of cain. 823, conductor878, terminal 901,

brush 902, the uppor contacts of tram 935,

brush' 936, torininal 937 through the 'Windin'g of thoystopping rolay (not shown) 'oftho sonder to ground. Relay 825 onorgi zcs in tracod. As soon as. an idle trunk is reacl1od,

charactorized -by the absenceof ground on its sloovotermnal, tho locking circuit of rolay 825 isoponod and that rolay reloascs, in turn' roleasing theup-drivo magnet 831,t0 bring tho district Soloctor to rost withits brushes 839, 840 and 841 on the terminals of tho soloctod idlo trunk; Tho roloase of rol ay 825 closes a circuit from battery through tho Winding of soquonce switch magnot 800, the right contacts of cam 834, the right back contact of 2 rolay 825 to ground as tracod for advancing soquonco switch 800 into position 9.

7 dopendont of rolay 825, which ground is maintainod until the soquonco switch loavos position 15%. With soquonco switoh 800 in position 9, a

circuit is comploted from battory through the 'right winding of rolay 825, lowor loft contact of cam 844, the right contact of rolay 821, the lowor right Contact of cam 833, to ground. Rolay 825 oporatos andclosos a circuit from battory through the 'winding of soqucnco switCh magn,t 800, uppor right contact of cam 826, right front contact of rolay 825 to .,ground as traced for advancing soquonco switch 800 into position 10, in which position it romains until all subsoquent soloctions have boon.complotod. In this position tho fondamental circuit oVor whichsubsoqu'ont ;-.soloctions are controllod extends from}brush 841'oor theupper loft and lowor right contacts of cam849, tho right back contact of rolay 850, thnco; over conductor 878 to the sonder, rturning ovortorminal 939, brush 938, tho uppor loft and loworright contacts of cam 905, brush 906, terminal ;907,con 'ductor 818, tholowor contacts of cam 851,to

r brush 840.,

Foll0wing tho completion of slections and tho advanco of thoincoming soloctor, current over the fundmental circuit is rovorsod and tho sonder is 13roparod for makingtalking soloction; .At this tinno, tho sonder incroases tho ;rosistanco in tho circuit of rolay 821 to such an extont that it roloasos, oponing tho circuit of relay 825, whichin turn reloascs, closing a circuit from battery.through tho winding of soquenco switch magnot 800 ovor the right Contacts of cam 834, tho right back contact of rolay825 toground astrace df0r advancingsoquenco switch 800 outof position 10 into position 11. .As soon as Sequonco switch 800roaches position 11,'acircuitv is ostablished for mgnot 800 Over the uppr right contact of Gain 826, .the uppor contacts ofcam 832 to ground at tho.uppor right contact of cana 833 for adv incingsoqucncoswitch 800 intopositin2. v

As soquonce switch 800 pasSoo into position 11, a localcircuitis stablishod forl;rolay 821 extonding, from battory .through; th o Winding of rolay821,tho uppor lofti"arid loWor right; contacts of cam .820 to ground at the lowor loft contact of Cafn 836 and ground is coni1ctod to the sonder ovefltholowoi*loft contact of cam 836, conductor 819, terminal 933, brush 932, pponcontacts .of cani 946, loft Winding of relay,9l5, loft back contact f-rolay 909, the uppor right contact of cane 934, bruslr93l, terminal 930 to battory in the sonder for advancing tho 'sonder for:

niaking talking Exoloction} Rolay 915 doos net, howovor, oporate in this circuit. At this' time the calling lino is connoctodfloxror tho lOwor contact of cain 815, through the loft windings of repoating coil 852, Ltho, uppor V contact of cam 816, and through theWinding of suporvisory rolay.827,thcrby oporating rolay 827 which establishoSa holding circuit for rolay 821 oxtondi1ig froni battory through tho winding of rolay82l, the front contact of: prolay 827, to ground at the lowor right con tact of can1 805. Rolay 821 is mairitainod oporated until the calling subscribor 'roloasos tho connoction.

In position 12 acircuit is ostablishod for rolay. 825 oxtonding from battory through the loft winding thoroof, tho uppor right con tactof cam 824, tho uppor loft contact 'of.

cam 823, condu'ctor; 878, thonCo as 'tracod through tho Winding of the Stopping. rolay of the sonder t0 ground. Rolay. 825 and tl o stepping rolay of thozsondor cpato 1n th1s circuit, rolay 825 closirig tho proviously traced circuit for advancing sequonc sWitch 800 out of position 12 and locking it'self t0 tho fundamontal circuit over its outer loft front contact and'tho upper loft contact of cana 824. SWitch 800 now 'adVancos' undor the control of relay 825 and in positions 12%, L

13% and 14% connocts ground over the right contacts of cam 848in shunt of,tho winding ,Oftho sonder stopping relay. .Tho position in which soquonco 'switch 800, cornes to, rost "is dtermined by the comitigrelays of tho 7 sendor in accordanco viththo talking solectic-n registration sot 1ip,by the sondorcode this .soloction, tho fundainontal circuit is oponod, thoroby.rolersing rolay 825 and Stopping tho soquonco switch 800 in the noxt stop-- pingposi tion. F0rtho purposos of this doscript1on it Will bo assumod that soquonco Swith 800 stops in position 14.. In this position the right WindingS' of ropoating coil 852 are connocte d ;ovor tho loft'contacts of Gains 849'and 851through' tho Winding of polarizod rolay 853 and the loft contacts of cam 845 to thobrushos 840 and 841 and thonco to the incoming soloctorx'fl Thec all od 1 i nois tostod by the final solector its normal condition. Downdrive magriet 535,uponenergizing, 110W drivSthe line u relay 206 and cause the operationbf relay ..finder shaft dOwnwardly into normal position, opening theholding circuit of .relay 515.- V when brush 518leaves coinmutator strip 517.n :=-The release of relay 515 then opens the cir- "cuitzof magnet535 t arrest the downward movement of the switCh shaft and connects battery toythe:winding of'relay 501 to mark circuits of thlihe finder 550 are riowzin nor-' the line finder as again selectable. All of the smal Condition *"With.sequenc-e switCh800 off-the district selector ,of Fig. 8 in position 18, a circuitis established for-the clowndrive magnet 864 of theline finder 880 which maybe traced from batterythrogh the Winding of mag- 7 7 net 864, thelower contact cf camr806,.-the; 2d outerleftfroht contact of relay 802:t0 grOurid at the uppr.left contact o-fcam 836. The

unagnet 864 nergizesin this circuit driving the :line finder shaft into normal position when: the holdingcircuit of rel'a 802 "is opened b brush 871, leaving commutator strip 8705 Relay 802 .thereupon rleases,

- opening the 0Pcrating circuit of inagnct 864 winding 0f magnet 866, left contacts of cam to arrestthmovement of the switch shaft. In position 18 a circuit is also-closed for the doWndrive magnet 866 of the district-seleC- ton 890 xtending from battery through the 824to ground at the right Contacts of cam 848. Magnet866causes the district selector {switch shaft-to be driveririnto normal posiin office B, the -start circuit 7 50, link circuit of Fig. 9 and districtcircuit funtion toconnect suchrhne w1th a desired lme in the same.mariner as previousl described' "in connection with theestablishment of a conjnection between the calling trunlr 555 and a desired line, y 7 Second dzz -ofigzndted in-oflce A Mitan aZZ links of the A group seming thelne group a7e bus and Zinc fimle1 550 :busy

- Upon the initiation. Ofanother call by alirie when there are no aVailablelink circuits and allotted line firiders of the A group normally serving such suhgroup of lines,.it beingiur- *ther assumed that the line finder 550 isbusy 7 serVing 'the call previouslydescribed, relay in the same subgroup as lineat a:=time start circuitover conductor 131 will look up 208 as pre'viously desCribed. As long as there.

are any.. idle auxiliary line findersthe'r Will" 'be: groundpotential on conduct0r 211, over the-back contacts of relay's of such line finders corresponding:t0 relay 514 and therefore 7 -upon the operation of relay 208 a circuit Will be established from ground on conductor 211,

over thecontacts cf relay 208, the-badrcm1- tact of stppi1ig magnat .212 of' sclector 200 to battery through the wi'nding 0f relay 213, thereby ei1ergiZing rela 213. Relay210 Will not operate at this time because battery potential over brush 209 and conductor 503 has been removed, at the :line findr550=which has been assumed to loe busy. Relay 213,up0n .operating,therefore closes a circuit for stepping magnt 212 fre n batterythrough the winding of'magnet 212, contacts of rlay 213 toground atthebaokcontact'of relay 210.

Magnet 212 then, operates, opning the circuit0frelay 213, which releases'in turn Opening the Circuit of'ina'gnet 212, whereloy magnet 212 advances the brush209 tothenext terminal of its bank, If this terminal is con 'nected toa c0nducto'r similar'to condu'ctor 503 which extends t0 a b us'y line finder, no batter Potenti al Will be found thereon and relay 210" will-remain deenergizecl. Therefore, upon the release of stepping magnet 212, the cir cuit bit relay 213 is again'established and r6 1213 213 Will gain Close the circuit of magnt 212. Magnt 212 and relay 213 Will 'the1e'' fore interact to advance the selectoi bi'iish 206 Will be cenergized and th closure of the a 209 another step. This operation continues 'until brsh209 encou'nters battey, Potential on a termirial of its bank,indicative of an idle line finder, Whenrelay 210 will'operate, open- VVhen the operating circuit of.1ely 210,be' conies effectie,-the lino relay of the selected lime finder corresponding to relayl50l also' operates and the call-then proceeds in the;

-manner prviousl -described.

j may occur that after Serreralcalls have been1n1t1ated1n theucalhng l1ne subgroup in Whichthe line 100 is located, utilizing all 03'? thelink circuits of the: A group andseveral .callis iriitiated in the szime calling lino suh group,'the chain circuit over came 424424 *w1llbe br0ken at the carn in this circuit cor- *responding to the idlelink circuit ancl'isclay 206 Will therefore not be operated. 'lhestart circuit 131 'will-therefore 'be extcndedfiovcr Ring the circuit of the stepping magnet'212 ;to arrest further advarice of the -s'elector;

thright back contact 0f relay 206*and Conductoi'226 to siich idle link circuit and thence :to*the start circuit of the linefinder prc-al- .lottedby su'ch link circuit; 

